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International CoUIicil for
the Exploration ofthe Sea
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CM 1996/S: 14
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DOESBLlJE.'VIDIING l\UGRATE FROl\1 PORCUPINE BANK
TO BAY OF BrsCAY AFTER SPA\VNING SEASON?
By
Carrera, P.(I); Meoode, M.(2); Porteiro, C(2).
AIld Mique~ 1.(3)
(1) Iristituto Esp~ol de Oceanografia. Aplirtado 130, 15080 A Coruiia (Spain)
(1) Institllto Espaiiol de Oceanografia. Apartado 1552, 36280Vigo (Spain)
(I) InStitUto Espaiiol de Oceanografia. Apaitado 291, 07080 PaIma de Mallorca (Spain)
ABSTRACT
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Duiing March-April 1994 arid 1996 two crUises have been camed out aroUIid Bay ofBiscay in
order to check movements of blue whiting using acoustic methods. These cruises consiSted in
a double coverage of an area from 47°30' N, 7°15' W to 430)0' N, 60)0' W along the French
and spanish continental sheU:biellk (200m to 1000 m isobaths). Whereas in 1994 a zigzag
surVey design with 20, nmi between peaks wasperformed, in i996 the surveydesign consisted
in parallel trarisepts "ith 24 nrill apart and, in both cases, noImal to depth contour.
mam
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The IruljOrity ofthe blue whiting from the Northem areas migrates to the
sPawning area
which is locat<.~d West of British Isles, lnain1y around Porcupine Bank, dtiring March-April.
After spawning, there is
exodus from this area to the feeding grounds. The main migration
route is iri Northward direction which has beeIl widelY reported but it is not kriOwD. if fish
commg froin the Bay of Biscay takes part in this migration. From this surveys, it cöu1d be
concluded that there are important movements of blue whiting arotind Bay of Biscay, lnain1y
on younger ~ and these seem to be in relation With a southward rDigration after spawning.
an
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INTRO DUCTION
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Blue whiting (MicromesistiuS poil/aSsau, Risso) is
important fish species in terms of its
abundance in the North AtIatitic. It has awidesi>read distribution along the continental slope in
the North AtIantici arid alSo in the Mediterranem sea. Contfary to the noriDal behaviour of
other gadoids, blue whiting is not a t)pical demersal specie, and speilds the major part of its
life with no noticeable relationShiP with the sea bouorn. (Zilanov.. 1980). This has enabled this
especies to be Studied by means of acoustic methods since 1972 (Anon, 1982). oDe cif the
most imPortani features ofthis species is its ability to migrate from feeding areas to spawning
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ones and viceversa. These movements in the North Atlantic are weil documented (Zilanov,
1980, Anon, 1982, Bailey, 1982, AIion, 1993a) and different acoustic SUlVey have been
carried out, especially in March/April around the weSt of the Biitish IsIes where the major
spa\'~ning stock is congregated over a relatively srIla1l area; after spawning, there is a rapid
migration towards feeding areas.
In the southem part of the distribution area, not orie attempt had been performed before to
demonstrate th~ movements of the bhie whitmg. Under the AIR projeet SEFOS (She/f Edge
and Oceanographic Studies), \vhose main objeetive is the study of the relationship between
the distributions and migrations of commercially impcirtant 6sh and the hydrography of the
shelf edge, the Instituto Espafiol de Oceanografia programmed tWo acoustic SUlVeys in 1994
and in 1996 to study the movements ofblue whiting afotind the Bay ofBiscay.
'Before this, in a meeting held in Vigo, the Spanish acoustic srirVeys carried out in 1991-93
\\fere analysed. These SUlVeys had a zigzag track ~ith 10-12 miles betWeen peaks, from 20 m
isobath to I 000 m isobath. Thc blue whiting distnoution in each SUlVey was studied by means
of geostatistical techniques using the integration values for each transeet as unit sampling. Thc
losses in precision are negligIole wheri. the distance between peaks increases to a lnaximum of
20 miles; this analysis was carried out by performing an experimental variogram with the three
cruises combined and testing the corifidence intervals as a perceritage of the mean, when
transects were eliminated both systematically and randomly.
Finally, the SUlVey were designed covering the shelf.edge (between 200m änd 1 aOOm) where
blue whiting are mainly distributed (Meixide et al, 1991). In order to check movements, the
area should be covered twice.
l\lATERL\L AND METHODS
The SUlVeys were carried out on board R/V ''Cornide de Saavedra". The acoustic trips were
performed over the Bay ofBiscay.(VIIIa,b,c ICES Divisions). Table I sun:imarises the main
features ofthese trips. Surveys design were in bClth cases nörmal to the depth contours, from
200 m to 1000 isobath,(figure 1). Besides, in 1996 in the Spanish area during the fust trip,
transects were extended to 20 m änd extra transeets were alsO :illocated in order to evaluate
the spänish fraction of sardine stock, but for this analysis this transeets were not used.
A Simrad EK-500 echosounder-echointegrator with a 38kHz split beam transducer was used.
In 1994 results ofthe calibration performed in November 1993 were assiirned whereas in 1996
the equipment was calibrated before the SUlVey accoi'ding to Foote et al (1987). Surveys were
conducted day and night at a ship speed of 10 knots. Acoustic back-scatterings (Sa values,
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expressed as m /nmi , Bodholt, 1990) were direet1y colleeted every nautical mile (nmi) and
stored in a pe, which controlled the main. settings ofthe echosounder. Geographical position
was also taken by GPS.
Biological samples were obtained in pelagic trawl stations to ideritifY bluewhiting arid its age
strueture. In each trawl station a random sample of 80 fish was sampled (len~ weight. sex,
maturity and citolith) and 40 were aged on board. This random sampling stfateg}r was adopted
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in order to obtain unbiased parameters (AD.on 1994) and to make the exammation of age
stmcture eaSier during the cruise.
.Changes in acoustic back-scatterings of blue whiting were studied by means oE geoStatistics
tools. The use of geostatistical tech.D..iques (Matheron 1971). and theii applicatians in fisheries
research, both for mapping atid variance eStimates, is wen documented iIi Conm (1985) aiid
Petitgas (1991, 1993) and has been recommended as a tool for the analysis of acoustic SurVey
data in Alion (1993b). The analysis was penormed applying the transitive theo.y on the
transect ciunUlated data. Besides another estiri:lation ofthe variance ofthe abundance estiIriate
was undertook using the intrinsie theory. on the Sli values asSigned far blue whiting in each
nmi. These analysiS were penormed using EVA vl.O (Petitgas and PiamplUt, 1993) arid
SURFER v6.0 (Golden Software, Inc.) packages.
Tri order to avoid problems with the geometry of the habitat in these aiialysis, the suiveyed
area was firstly divided in three zones as folIows:
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North France: from the upper surVeyed liririt to 45°N
South France: from 45° N to the Spamsh-French border
Spain: from the Spanish-French border to 6°15'W
These Irulin areas were chosen due to the different direction of the coiitlnental shelf-break
(225° degrees aprox. in North France, 0° in South Fnmce and 90° in Spain), Where blue
\...hiting is mainly concentrated.
~fean 5 a values ofeach zone and the sllIface cifthe blue whiting distnoution area were used to
estirrulte the abimdance. according to Nakken and DOmInasnes (1975). The following
TSlLength relatioiiship (AD.on, 1982) was used:
TS = 21.8 * log(L) -72.8 (dB)
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Changes in popUlation age Strueture as weIl as mariiritY stages using a key of six empirical
stages (Abaunza et al, 1995) weie alSo checked.
RESULTS
total of 811 and 762 nmi respectively were surveyed in 1994. In 1996, 640 nmi were
surveyed during the fust tnp and 580 ru:Di duIing the secönd. Fig. 2a atid b. Show a
proportional representation of the data. Those nini with iill value are represented by b13ck
disks.
A
As in previous surveys, blue whiting distn'bution is related to the contiIiental shelf-break. in
both surveys the eXternal limit of the distnoution seemed to bei reached. llH:re only were
positives values at the end of two transeets located iri th6 nofthem part of the area of the
second trip undertaken in 1994. Over the continental sheIt: the inner limit appeared to be close
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to the slope. This "Yas clearer during the trips performed in 1996 than in those carried out in
1994. Although there was a continuit}r behveen transects in North France during the 1994
survey, meaning that the inner limit was not yet reache<!, these values were, in general, lower
and, therefore, we can assume that the limit was reached.
Within each area and trip there were a few samples with high values. These values had an
important contribution on both arithmetical mean and variance. The global estimate and its
precision are therefore determined by a few very large values (Petitgas, 1993). Whereas in
South France and Spain there is no clellr zonation ofthese high values, in North France during
the second trip of the 1994 survey, they appeared to be concentrated on the northem pari of
this area. In order to apply the intrinsie theory, the assumption ofno border effects was made,
however.
Nevertheless, due to the ske\\ness ofthe frequeney distnoution ofthe data, variograms were
firstly performed on transformed data (logarithmie transformation). These variograms did not
show clear anisotries and therefore isotropies variogramS were conStructed. Besides, these
variograms were used to clarify the spatial Structures found over raw data.
Figure 3 shows the isotropie experimental variograms for the raw data, rescaled to the
variance value, for each zone and trip. Total number of data, total number of data inside each
area of blue whiting distribution area and total of positives valties, range, arithmetical. mean
2
(Sa)' surface (nmi ), fitted variogram models, c.v.'s and degree of coverage (Aglen 1982)
for each zone and trip are shown in Table 2. Due to the low level of samples, those vanograms
corresponding to South France in 1996 werc~ no constructed.
Between trips, they were important changes in the surface of the distnoution area of blue
whiting, which would probably be the most importärit fact. These differences are important in
North France and in Spain, with changes of about
double of the total sUrface. In South
France the area seems to remam almost the same. Changes during the survey carried out in
1994 were contraryto those found in 1996. Whereas in 1994 the.surface increased up to the
double in both areas, North France and Spain, from the fuSt to the second trip, in 1996 there
was a decreasmg in the same way from the fust to the second trip.
the
Mean Sa values seem to be stables when the sUrface of the distnoution area change. In fact,
these merin values were almost similar in North France in 1994. and with differences lower
than 15% in Spain in both surveys. 0nJy North France during 1996 showed changes in both
mean value and surface. On the contrary, South France, which presetited negligible differences
in surface between trips, showed differences in wean values higher than 50%.
Spatial structures were performed using 1.5 nmi as a unit lag. Due to the nanower distnoution
ofblue whiting around the slope and the distance between trarisects, these variograms show,
in general, a low or even lack of pair values at certäin lags. This feature could give spurlous
sPatial structures. In order to avoid thiS problem, the experimental varlograms were fitted to
models using as a reference point those tags with aleast of 30 pair of values. Variograms
showed a spatial structure whose sills seem to be reached at 8-12 nmi. Tbe fitted models were
spherical and exponential and in some cases, the presence of a nugget effeet was also
observed. As a consequence ofthe different distance between transects in each survey, models
constructed for 1994 fitted better than those constructed for 1996. Coefficient of variation in
1994 ranged from 10.74% to 26.65%. In 1996 the coefficient ofvariation varied
15.11%
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to 35.'09%. Nevertheless the differenees in varianee of estunations agree With the differenees
in the Stirvey. design pelformed in eaeh year. Besides" these differences agree With the
differenees in degree ofeoverage fowid in eäeh area arid year.
Baek-seauering values were aisoanälysed by means öf the transitive theory. In 1994 an
independenee benveen transeets \vith a fixed intertranseet distanee of 10 rimi was aSsWned.
Cumulated transect values for eaeh trip arid year are plotted in Figure 4. As it was pointed out
above, there \vere imPoi1:illi differenees between trips. In 1994 North FräIice and Spam show
an impoitant increllsing from the first to the seeond trip. In 1996 there was a generai
decreasin~ in.the whole area from the flrst to the seeond tIip.
Experirriental covarlogramS and the fitted models conStrueted are shown in Figure5. The
number of transects, intertransect distances, range, arid mean value of the cumulated values
and the fitted eovariogram models and ~eir vaiiance eStüruites and c.v. 's are shoWtJ. in iable 3.
Changes m: mean values among trlps and areas were eieu. The moSt important changes ,vhieh
,Vill be further retlected in changes in both nUmber of fish and bioIIJ.asS occuiTed in North
Franee arid Spain.
Fitted models were no directly inferred from the variogiams models fitted in 2-D. NeveItheless
the fitted models were performed taking into account the spatial charaeterlstics whieh were
modelIed in 2-D. The models seem to fit well With the experimental covanogramS. It appears
to be some inconsistencies between the estiniait~d variances in 2-D and those esti1ii3ted in 1-D
in some areas and trips, however. These are alSö refleeted in, the coefficient of variation
estiniated for the nvo methods. The areas in which there were differences between c.v.'s, the
eStitruitions calcwated by the ti:illsitive method (ie. Oll covariograms models) were lower than '
those caleulated by thc intrinsic method (te. on vanograrns models). These differences ,vill be
discussed further.
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The population strucnire fomid iri 1994 was d.uferent to that found 1996. Age group 3 was the
most abundant in 1994 whereas in 1996 age 1 arid 2 represented up to 95'ofthe popUlation. lIi
1994 it seems that the major change occurred iri the totaI nUmber offish (Figtire 6) remanding
quite stable,the age structure ofthe popUlation from the first triP to the sccond iri the different
areas. In this year,the iriciease from the .first to second tIip was higherin. Spain; where age
group 3 became alSo more import3nt. During 1996 there were important differences in both
niunber offish and age stmcture between triPs. Thc decreasing m. number of fish from the firSt
to the secorid trip was also accoriIpamed mth a change in the population structure. ThiS was
so cIear in North France mth age grotip i and in Spain mth age groul> 1. In North France age
group 1 had a lo,v increase froni the firsi: to the second trip Whilst age group 2 decreased from
11 nilllion fish to 3 inillion fish. Iri Spam age group 1 decreased from 52 niillion fisli to 8
million fish; in this area the decrease of age group 2 was only abotit Ö.7 inillion fish. The
deen~ase ofage group 2 in North France and age group i in Spain froni the first to the second
trip without an increase of these age gi-oups during the second tnp in others sWveyed areas
SuggeSts that there was lllSo movements outside the studied area.
Mean fish density expresse<! as anumber offish per square nmi in each area and trip iS shoWn
in Figure 7. In i 996 Spain shows high values of fish denSitY compared to those estimated for
the other areas and trips. Changes in fish density between tnps were alSo deteCted in both
surveys in Spain and iri Noftb France in 1996.
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During the first trip of 1994, bIue whiting was riiainly distribuü:d along the continental sheIt:
break; in addition in Spairi it was also found on the continental sheI.t: elose to the slope.
NevertheIess this pattern of distribution was different in North France dtiring the second trip
of 1994 and in both trips of 1996. In these trips its distribution spi:eadedfurther offshore in a
peIagic Iayer, around 150-250 m in 1994 and 250-350 m in both triPs of 1996.
The mean Iength ofbIue whiting is described to be reIated to depth (Balley, 1982). This seems
to be tme and the Kolmogorov-Smirnov test applied to the fishing stations performed in 1996
showed statistical differences among fishing stations. NevertheIess during the first trip of this
survey a good correlation between mean Iength and depth appears to be found (eoeL corr:
0.89, Figure 8) but during the second trip this relaiionShip was 00 so cIear (eoeL corr.: 0.13).
In 1994 all the specimen were matur~ (Figure 9). Duririg the first trip stage 11 (deveIoping)
\vas predominant, with a 89% in Spain; in addition in t.hiS area there was a 36% of specititen in
stage VI (resting) and in North France the 30 % weie in "active" stages, that this: stages m,
VI and V (Prespa\~ning, spawning and postspaWnitig). DUrlng the second trip almost all the
specimen were in stage VI. In 1996 an importani part ofthe population were immature, being
71 % in Spain during the first trip. The major part of the matuie specimen were in stage V.
During the seeond trip, this stage was also predominant in North and South Fnmce whereas in
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Spain, there ~as still an important proportion of immature Specimen (47%), and Stage VI
represented 31 %.
DISCUSSION
Since 1960, blue whiting has been kno\\n as an important migratory species in the North
Atlantic (Balley, 1982). While in summer and autiUriIi the species is widely diSpersed over
most ofthe Norwegian Sea, important concentrations ofbIue whiting begin to fOIm at the end
of the year. By February, beginning of March adult fish are concentrated aro~d Porcupine
Bank where they spawn. After the spawning season there is an exodus from thiS. area. From
the North this movement is well documerited. Monstad and Belikov (1993) found an
important rate of migration, and t.hiS main spawnmg area becaine almost empty at the
beginning of April which it is one month Iater'after the peak spawning. NevertheIess, these
surveys never reach \vaters further south than 49° N, so the possibility of migration
southwards was unkiJ.own.
From this study, quick changes in both number offish and population strueture ofblue whiting
appears to be clear. In 1994 the age strueture found and the differences in niaturity stages
together with the changes in fish abundance, could indicate a southward moveinent after the
spa\\nmg season from the mainspawning ground. NeverthelesS this movement of adult fish is
scarce in comparison to that undertaken northward.
On the other hand results from 1996 Yv'ere different from those of 1994. Juvenile fish (age
groups I and II) were predominant and there was an important deerease from the first to ,the
second trip. The main changes in terms ofnumber offish oecurred in North Franee related to
age group ri and in Spain related to age group I. Both age groups seems to be disappeaied
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from the studied area. Besides, this age graups have an important proportion of im.m3ture fish
(82% atid 52% from the iiiaturity ogive, Anon, 19~~) ,which would not D:l.ake thiS spa\wirig
migration. This also agiees with the Iow number offish in stage VI(sPent)foiind in both trips.
Conceming to fish oider than two years, thefe was a decrease in North France from the first to
the second trip whereas in Spain there was an slight increase. Iti addition, this year the peak of
the spa\..ning was earlier llIld the poStspwaning migi-ation might be take earlier than usmu
(Monstad et al, 1996). Tbe most noticeablefeature are the quick changes in bath age struCture
and number offish in a relatively sort periods oftime.
Changes in fish abwidance in North Frarice an<! .South France seems to bei: related to an
mcreasing in the distribution area räther than a change in fish densitY expressed as a nW:Dber of
fish nIni·2• In 1994 \\'hilst the total number offish increased twice, there was DO changes in.tish
density between trips. In 1996 in North FrllIlce there was also decreasing fram the firSt to
the second tnp. In Spain the changes in fish density were more important mboth sUiveys,
being higher than a 200%. The ireat values found in 1996 seemS to be related to the preseD.ce
of you.ng fish. At leaSt in the studied area; blue whiting appears to be associated to the
continental shelf-bre.alc. Once the munber of fish is increasing, the distribution area iS spreaded.
Iti France the area is extending to deeper \vaters, in a pelagic Iayer at around 200-300 m, With
almoSt no presence on the sheli In SpllIlish wasters, as weil as iri. France, it is Inainly
distributed on the slope, but it extetids its diStribution area thfmlgh the coritinental shelf until
iOO-150 m, with almost no extension in a pelagic Iayer likci: that found iri France. Tbe Spanish
shelf is narrower than the French shett: but it is also deeper, going doWn as far as 250 m in
comparisoD. to the 150 m of, the French. This topographical difference may explain the
presence of blue whiting over the spllIlish shett: but it would not explain its lack of extension
in a pelagic Iayer like that iIi French waters. According to Porteno et al (1996) the different
hydrod)namic activity coUld explain thiS different behaViour ofbrue whiting.
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From the analysis of the previous surveys (spring 1991-1993), the range of the spatiaJ.
distribution of the variogramS of blue whitirig is found to be 10-15 nnii. These values agiee·
Withthose famid dUririg these surveys. Tbe variograms models perfomied in 1994 cruise ga-ve
good fitting to the experimental ones. Olle to the lack ofpairs at certain lag~ variograms from
South France llIld Spain showed some problem to be fitted. In addition, these two models
gave a coefficient ofvarlation higher ihlin the others. Tbe same problem about the lack ofpair
values at certain lags in the variogi"ams aroSe in the. second trip of 1996. Tbe models iIi this
trip \",ere fitted with ranges of about 8-12 nmi, in which the range of the Spatial struCnires is
eXpected to be found. Since models performed iIi 1994 dufing the second iiip and in 1996
during the flrSt one had range around 8-12 nini, fitted models with this range peiforiried for
the fust trip of 1996 might be appropriates. .
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EXperimental covanograms were fitted \Vith. regardirig tothespatial foUIid the variograms.
Covariograms
South Frarice in 1994 only had 6 transeets. In addition cumUlated values
wen~ similaf, specially duriDg the secorid inp. noth featUres might contribute to the apparently
continuitY ihat spatial structures pfesent. Whereas the spatial struCriUes ofblue whiting have a
range about 10 nmi, the distance between transeets during the 1996 crUlse was 24 nmi. Ifany
.spatial structUre existed at lower distances thau 24IIIn4 it would be mask, and therefore, any
estiInation ofthe varlance based on ihis model coUld be biäsed.
of
. Tbe narrower distribution of blue wWÜtig in certam areas of the different trips and the low
level of sampling inside these areas, in both number of tiansects
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arid number of nmi Steamed;
could lead to spurious spatial structufes in both covaiiograms and variogramS and hence the
differences in coefficient of variation calcUIated by intrinsie aIid transitive methods could be
explained.
Nevertheless, in order to obtain abundance estimates with a reasonable good precision and at
least ,from this area, a survey design with a distance betWcen transects ~f 10-12 nmi would be
appropriate.
In spite that important blue whiting movements around the Bay of Biscay have been detected,
the relation with a postspav.nmg migration is scarce. It seems that the southward
postspaWning migration fram the Porcupine is undertaken for a few young mature specimen
(mainly age groups II and Ill). But this migration is sparse compared to that undertaken
northward (Monstad et al, 1996).
In addition the Spariish monthly catches of blue whiting remain stables throughout the year
and the total yearly catches appear to be also stables at around 32 thousand tonnes since 1981'
(Anon, 1996). The fisheries are mainly developed on young fish (age groups 0, land II) and
the age structure remains also throughout the year. The same age structure iS also found in the
acoustic surveys carried out in spring and in the bottom trawl surveys carried out in fall.
In absence of adult fish as well as the lack of significant spawning grounds in this area
(Porteiro et a/, 1996), a young migration or a southward larvae drift (Fraser, 1958) could be
suggested. The presence ofjuveniles in this area has been reported (Maucorps, 1979) and has
also detected during these surveys (Carrera
al, 1996). There is, however, some evidences
about a differential pattern of distribution of blue whiting. DUring the spawiUng season
(spring) the length distribution in Porcupine Bank norinally ranged from 19 to 40 cm
(Monstad and Belikov 1993), with 28 cm as mean and a unimodal length. frequency
distribution. During the feeding season (summer) in the NOrWegian sea, the length distnoution
can present different modes, corresponding to the 0 group and the others at lengths between
22-28 cm (Jacobsen, 1990a-b, 1991, Monstad and Dominasnes, 1990 and Monstad, 1990,
1993). There is, however, a discontinUity between these, corresPondirig to length group from
16 to 22 cm,. which are the main length groups found in both the Spanish and Portuguese
fisheries and in the acoustic surveys in Spain (Meoode et al 1991, Amin 1993a). Also in
catches further north than 50° N the length groups between 16 ta 22 cm are relatively scarce
which is in agreement with this theory. This kind of behaviour cän be seen in other species
such as horse mackere~ which presentS· a poor distribution cf specimens between 19 to 22 cm
length classes in the Spanish fisheries, in coinciderice With the firSt sexUal manirity (Abaunz.a et
al 1995).
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According to that, it could be better to emphasise the presence of a nursery area in this area as
a result of a drifting processes together with a juvenile migration rather than an adult
postspawning migration. Ta demonstrate this, more information is needed and further surveys
should be carried out in sUmmer when the juvenile 3:fe fully recruited.
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Acknowledgements
\Ve are indebted to the staff who took part in the SEFOS 0394 cruise. Also our
acknowledgements to the crew of the R/V "Comide de Saavedra". We wish also to thank
lohn SiInmonds and Dave Reid who helped us to design this survey lind to the anonymous
referees who helped improve a first draft presented at the Fisheries lind Plankton Acoustics
Symposium held in Aberdeen in lune 1995. This study was developed under the frame ofthe
EU-AIR, SEFOS programme (AIR2-CT93-1105).
REFERENCES
,
.
,
Abaunza, P., Fariiia, A C. and Carrera, P. 1995. Geographie variations in sexual maturity of
horse mackerel,- Trachurus trachurus (L.), in the Galician and Cantabrian shelf Sei' Mar., 59
(3-4):211-222
.
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Aglen, A 1989. Empirical reSults on Precision-Effort relationships for acoustic surveys. ICEs
CM 19891B:30.
Anon 1982. Report ofthe international acoustic survey on blue whiting in the Norwegian Sea,
luly/August 1982. ICES CM 1982/H:5
<
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,
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Anon 1993a. Report ofthe blue whiting assessment working group. ICES CM 1993/Assess:4
.Anon 1993b. Report ofthe workshop on the applicability of spatial techtiiques to acoustic
survey data. ICES Cooperative Research Report, no 195. 87 pp.
.
Anon 1994. Report ofthe workshop on samplmg strategies for age and maturity. ICES CM
1994/0: 1, Ref ,:G,H,J.
•
Anon 1996. Repolt ofthe blue whiting assessment working group. ICES CM 1996/ASsess:??
Balley, R.S. 1982. The population biology ofblue whiting in the NOlth Atlatitic. In Advances
in marine biology. Vol 19, Academie Press.
Bodbolt, H. 1990. Fish density derived from echo-integration and iri-situ target Sirength
measurements. ICES C.M. 19901B: 11, 15 pp.
Carrera, P., C. Porteiro, and L. Valdes. i996. Depth lind spatial distribution ofblue whiting
juveniles iri Bay ofBiscay. ICES C.M. 1996/S: 15
Conan, G. Y. 1985 Assessment of Shellfish Stocks by geostatisticaJ. techniques. ICES CM
1985/K:30.
Foote, KG., Knuds~ H. P., Vestnes, G., MacLc:nnan, D.N. änd SimInonds E.J. 1987.
Calibration of Acoustic Instruments for Fish Density Estimation: A Praetical Guide. ICES
Cooperative Research Report No. 144.
9
Fraser, 1. H. 1958. The d.rift of the planktonik stages of fish in the northeast Atlantic and its
possible significance to the stocks of corrimercial fish. ICNAF, Special Publication no 1, 289310.
Jacobsen, 1. A 1990. Acoustic swveys on blue whiting north of the Faroes m
August/September 1988 and 1989. ICES CM 19901H:33
Jacobsen, J. A 1990. Acoustic swvey on bltie whiting north of the Faroes in
August/September 1990. WD to the ICES Blue whiting assessment working group meeting.
Coperihagen 1990.
Jacobsen, J. A 1991. Blue whiting swvey north ofthe Faroes in August 1991. WD to the
ICES Blue whiting assessment working group meeting. Bergen 1991.
Maucorps, A 1979. Le merlan bleu.. Seien et Peche. Bulletin d'Information et de
Documntation de l'Institut Scientifique et Technique des Peches Maritimes. No 294, 3-13
•
Matheron. G. 1971. The theory ofregionalised variables and its applications. Les cahiers du
CMM, 5, Ecole Nat. Sup. Mines Paris, Fontainebleau, 211 pp.
Meixide, M., Carrera, P and Miquel, 1. 19~1. AcouStic abundance estimates ofblue \vhiting
offthe Spanish Atlantic coast in March"ApruI991. ICES CM 1~91/H:29.
Monstad, T. 1990. Report on blue whiting swvey off the Norwegian Coast in November
1989. WD to the ICES Blue whiting assessment working group meeting. Copenhagen 1990.
Monstad, T. 1993. Observations ofblue whiting during sumnier 1993. WD to the ICES Bille
\vhiting assessment working group meeting. Torshavn 1993. ICES CM 1993/Assess:4
Monstad, T. and Dommasnes, A Observations of blue whiting in the Norwegian Sea,
Summer 1990. WD to the ICES BIue whiting assessment working group meeting.
Copenhagen 1990.
Monstad, T. and Belikov, S. V. 1993. Report ofthe joint Norwegian"Russian acotistic swvey
on blue whitirig, spring 1993. ICES CM 1993/H: 10.
Monstad , T. S., V. Belikov and E.A Shanirai. 1996. Report ofthe joint Norwegian-Rusian
acoustic swvey on blue whiting during Spring 1996. ICES CM 19961H:12
Nakken, o. and Dommasnes A 1975. The appllcation for an echo integration system in
investigations on the stock strength of the Barents Sea capdm (Mal/atus vi/losus, Müller)
1971-74. ICES CM 19751B:25
a
Petitgas, P. 1991. Contribution geostatistiques la biologie des peches maritimes. These
doctorat, Centre Geostatisteque, Fontainebleati, 211 pp.
Petitgas. P. 1993. Geostatistics for tish stock assessments: a revIew and an acoustic
application. ICES Journal ofMarine Seience, 50: 285-298.
10
•
Petitgas, P. and Prampart, A 1993 EVA (Estimation VAriance). A geostatistical software on
ffiM-PC for structure characterization and variance computation. leES CM 19931D:65L
Porteiro, C., Cabanas, J., Valdes, L., Carrera, P., Franco, C. and Lavin, A 1996.
Hydrographie features and dynamies of b1ue whiting, mackerel and horse mackerel in the Bay
of Biscay, 1994-1996. A Multidisciplinary study on SEFOS. ICES C.M. 1996/S: 13
Zilanov, V. K 1980. Short results of the Soviet study of b1ue whiting (Mieromesistius
poutassoy, Risso) eeology in North Atlantic. ICES CM 1980/H:32
11
Survey
Trip
SEFOS0394
First (ft)
SEFOS0396
Design
Date
CTD~
FiIDing~
NoTransed
zigZBg
34
10
Seeoo.d(~)
19-25104
20nmiapart
34
9
First (ft)
21-29/03
Parallel
22
12
7-13/04
20mniap~
22
9
19/03-14/04
Seccnd(~)
80
7&
Table 1: Main features ofthe cruises
No Inside
Trip
North Fr3l1ce
1994 ft
307 102(94)
0-7400
1994~
325 223(220)
345 166(135)
315 101(91)
0-16000
0-7000
0-4000
12356(55)
127 62(61)
58 10(9)
588(7)
0-4000
0-1600
0-3700
1996 ft
1996~
South Fr3l1ce
1994 ft
1994 !'t
1996 ft
1996~
1994 ft
1994 !'t
1996 ft
1996!'t
Spain
No
Range
Area
Mean
Variogram model
Area
895.04
926.74 Exp(1.22E+6; 10)
909.96 2012.21 1.7SE+5 + E:'q>(1.9E+6; 12)
741.87 4052.55 Exp(l.59E+6; 8)
422.97 2377.75 2.0e+5 + Sph(1.9E+5; 12)
var~
c.v.
d.c.
21796.25
18916.38
26114.88
7750.12
15.11
21.78
20.81
3.35
4.97
2.61
2.07
(U,OO
644.11
334.92
880.00
312.50
1.0E+5 + E.'q>(6.3E+5;10)
1.0E+4 + Exp(8.9E+4; 12)
n.a.
n.a.
29454.84
2963.44
n.a.
n.a.
26.65
16.25
n.a.
n.a.
2.38
2.74
0.81
0.66
38168(66)
310 141(136)
23799(89)
0-2500
0-2000
0-3800
344.28
657.90 ExP(l.S3E+5; 10)
415.S0 1207.44 1.0E+4 + Exp(1.39E+5; 8)
606.16 2608.79 Sph(7.84E+S; 12)
4322.06
1990.S5
2325S.S0
19.10
10.74
25.16
2.S7
4.06
2.04
20765(61)
0-10000
606.92
1361.70 8.0E+.5 +Sph(8.3E+.5; 12)
45348.69
35.09
2.09
553.41
511.73
151.00
148.76
16.49
•
Table 2: Estimates ofrelative abundance using the intrinsie theory splited by area and.
trip. Ft and st means fust trip and second trip respectively. Number of data for the total
area, number of data inside the delimited area ofblue whitng distribution with number
of positive values in brackets, range and mean value (Sa values) and area (surface
expressed as nmi2) of the delimited area, fitted varlogram. model and its varlance
estimate and coefficient of variation and the degree of coverage (No data inside
arealsquare root ofthe area)
Area
•
Trip
Distanc:e
No
Range
Mean
Covariogram model
Sph(8.4E+9; 10)+Sph(7.S8E+9;110)
Sph(4.13E+IO; 12)+Sph(3.6E+I0; 110)
Sph(5E+9; 8)+Sph(1.69E+10;110)+Sph(2.4E+IO; 288)
Sph(1.05E+9; 12)+Sph(4.4.5E+9;288)
2.218+10
var~
1994 ft
1994 !'t
1996 ft
1996!'t
11
11
12
12
10
10
24
24
300-295S0
S50-67550
600-23949
400-8050
8299.4S
18447.27
10262.42
3564.17
South France
1994 ft
1994 !'t
1996 ft
1996!'t
6
6
2
2
10
10
24
24
1190-90S0
2610-4375
2100-6700
1000-1500
6011.67
3460.83
4400.00
1250.00
Sph(1.0E+S; 10)+Sph(2.6E+9; 60)
Sph(1.0E+7; 12)+Tri(7.3E+S;60)
n.a.
n.a.
1.33E+{)9
2.21E+OS
n.a.
n.a.
Spain
1994 ft
1994 !'t
1996 ft
1996 !'t
17
17
S
S
10
10-5040
50-6880
S00-22870
1000-16650
1377.12
3450.88
7501.25
4943.75
Sph(2.6E+S; 10)+Sph(3.1E+8; 170)
Sph(6.5E+S; 8)+Sph(2.25E+9;170)
Sph(5.3E+9; 12)+Sph(8E+9;4S)+Sph(1.0E+IO; 192)
Sph(4.0E+9; 12)+Sph(2.7E+9;4S)+Sph(2.2E+9; 192)
6.96E+08
2.93E+{)9
1.11E+11
6.918+10
North France
10
24
24
Table 3: Estimates ofrelative abundance using the transitive theory splited by area and.
trip. Ft and st means fust trip and second trip respeetively. Number of transeets per
area,distance between transects (nmi), range and mean value (Sa values), fitted
covariogram. model and its variance estimate and coefficient ofvariation.
12
8.20E+1-,
1.25E+l
1.80E+I0
.------------~
~~-~-~--
-
------ ----
--~-
-- - - - - - - - - - - - - - - - - - 1
48°'r---'---..L.----J..----.:;;:-;f-----'--_--'
Figure 1: Acoustic tracks in SEFOS 0394 (above) and in SEFOS 0396 (below)
13
-+
...L...-_ _
48°'+-----'-----'------.;:--~---...........- - - - ' - - - -..........- - - _ t
o
o
o
o
•
o
o
7°
6°
5°
594
0-500
126
500-1000 39
>1000
52
o
345
0-500
238
500-1000 102
>1000
79
4°
3°
2°
1°
0°
Figure 2a: Proportional representation of back-scattering. The zeroes are denoted by blak disks. Above SEFOS 0394
first coverage and below SEFOS 0394 second coverage
14
•0
407
• ~OO
129
0500-1000 47
0>1000
57
7°
6°
5°
4°
3°
2°
1°
0°
48°·;------''------'----.;:---;-;t---.......- - -.........---..L....----t
• 0
594
• Q.500
128
0 500-1000 39
0 >1000
7°
6°
5°
52
4°
3°
2°
1°
0°
Figure 2b: Proportional representation of back-scattering. The zeroes are denoted by blak disks. Above SEFOS 0396
first coverage and below SEFOS 0396 second coverage
15
3
2.5
§:
~Oll
2
1.5
0
~
0.5
lag.
SEFOS 03114 SECOND TRIP
3
2.5
§:
e
~
2
•
"
"
.
•
:
··
I..... sp
•
·" '
.
"
,'..
..
:
..''
~
•
+··NF
··.··SF
I! 1.5
Oll
0
~
JIIA '••~.
~•••••
........ •.
..l1li
0.5
l1li
liA:',.'.
..~.;~ "'!' •
.a
:
,
10
....
.. .....
'
......
'." •• t...~~,
·
:'
.
'
20
••••
50
40
30
60
lag.
·..
SEFOS 03111 FIRST TRIP
..
to,' •
.....
,
3
,..•
"NFI
·· ...sp
2.5
§:
e
2
1 ::.
,,
,,
"
",
,.
I, ••
· .' .
..•. .'.'. ,,
..
•
..
'.... ..., .., .. -
• I'
•
'
'
'
..r.. ....."••,.. .,
I! 1.5
g'
j
~
:
:~
~
0.5
.,.
I
. . . . . . . . . . :·,.Al.
~
••••
' .. ",,' • • :'tI.
:
..
, ....
,,, ....
, ..
,, ....
f-r
',:
~
i
\
1
.~
:..
:
••
0
0
10
,
30
20
50
40
60
lag.
SEFOS 03111 SECOND TRIP
;'1"' +. 'NFl
3
:
"
:.
§:
e
.....:.
.::: ··.··sp
•
''..
2.5
t,
2
I!
1.5
Oll
~
..
..'
~
0.5
0
0
:•
•
10
:
..•.'.
'
"
~"'. ~
20
30
..
.,
I,t
. ""
.~:
·:'. .• ..
:
·," ..
· .
: .~.
~
,
:~
'."
'.
'.
,
t:•
...•. •••, ..• :: .,.
0
•
... :
40
:
50
60
lag.
Figure 3: Experimental variograms ofthe raw data. Semivariance values are rescaled to the variance
16
70000
r-----------------------------------------.
OFT
60000
North France
South France
OST
Spain
50000
40000
30000
20000
1
2
3
4
5
6
7
8
9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34
transec:ts
e
25000
II
OFT OST
20000
Nortll France
South
Spain
France
15000
E
Ir
10000
5000
0
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
Transects
Figure 4:
Cumulated fish back-scattering values along transeets. Above SEFOS 0394 and below SEFOS 0396.
FT and ST mean first trip and second trip respectively
17
,
1994 First Trip Spein
1994 First Trip South Franc.
1994 FirstTrip North Franc.
I
tOEIO
o
/\~
:
,
/\
.5EO'J
:
•
'0.
~
'e-~''I!
toE08
2E08
~.,
·····.9....
oEool--IO.-00---,,30,...OO----:50~.O--O--:70"'"OO~-..
~OO:--,:.,1O~.OO::-1
00,00
20.00
40.00
60.00
80.00
OE01
~'.,
10.00
30.00
.01W:ll--:C20"'00~--':':"':":.00~~-1OO=.0':':0"---""MQ";:00':"'..I;Lo.A..-1
50.00
2000
lOOOO
40.00
0000
40.00
00.00
1994 S.cond Tri South Franc.
1994 Second Trip North Franc.
8000
120.00
'jG.().OO
1994 S.cond Trip Spain
3.0
,9,.
'0.
•
''1\''
'g •
.g.'l
0 •••
O··.Q •.
.-9.
10,00
00.00
30.00
20.00
10.00
00 00
i.0.00
lO.OO
'50.00
20.00
~.OO
20.00
40.00
"0-')0
1996 First Trip North Franc.
OE1O
8E1O
\
.5E1O
il".....
'"o::
'0 ••, ''9,
'.
10EtO
r
OE
O.0IEOC......,"'.-00-""":7""OO...,...,-12O-.00---,.."•"..,.00,.........,...,-..,:;:",..-""--1
0000
t8.00
96.00
"4.00
moo
""-00
1996 Second Trip North Franc.
1996 Second Tri S ein
•.a.····e····.e...
2LOO
72.00
".00
Figure 5:
120,00
~.OO
Mt.OO
0000
'.00
4800
E.xperirnental covariograms ofthe rawdata and fitted models for each area and trip.
18
""-00
80.00
""'.00
_ : lIonh Pran..
_ : 80uth fran..
1600
1600
1400
1400
1400
1200
1200
1200
I~I
1000
800
600
1:1
1000
800
600
800
600
400
400
400
200
200
c:n
0
111
W
V
VI
VII
I~I
1000
200
0
_:8paln
1600
111
W
I
V
VI
VII
_ : lIouth Pran..
10000
11000
9000
9000
8000
8000
8000
,
7000
7000
7000
;
1=1
!KlOO
....
'0
10000
1:1
6000
~ooo
4000
3000
3000
3000
2000
2000
2000
1000
1000
1000
0
0
V
VI
VII
111
W
VII
V
VI
VII
. - - ~2194
~OOO
4000
W
. VI
I~I
6000
4000
111
V
_:lIpaln
10000
6000
W
111
.!
.
I····
I
n
I'
111
W
Figure 6: Nwnber offish (millions) by age group for each trip and area. (FT and ST mean first trip and second trip respectively.
V
VI
VII
1994
fCFTl
~
1996
20000
15CXXl
1cxxx)
NF
SF
NF
SP
SF
Areas
Figure 7:
Mean density (Million fish by squere nmi) for each area and trip
20
SP
•
24
22
• •
•
.." 20
Secondtrip •
(coef. corr.: .1?~ ••••••••••••••• _
6
... -_ .. -
~
"
i
18
•
•
16
14
75
150
225
300
Deplll
•
Figure 8:
Mean lengthlDepth relationship during SEFOS 0396 survey
21
r----------------------------
----~----
Fht trtp
1
1
075
0.75
~
0.5
Secondb1p
~
05
ISISF
DSF
OSP
CSP
025
0.25
~
0
I
11
111
n
J'""'1
IV
V
fb
0
VI
I
11
111
MMwltyatllge.
1
V
VI
Secondlrtp
Fhtb1p
I
IV
-....y-
1
0.75
075
[;]
05
DSF
~
05
&ISF
OSP
CSP
0.25
025
O[
.J1
I
11
~
111
n
~
IV
V
0
VI
n
I
-..nty_geo
r1
11
111
IV
V
nn
VI
-..ntyo_
Figure 9: Maturity stages for each area and trip. Above 1994, below 1996. NF, SF and SP mean North Frane,
South F~ance and Spain respectively
22
•